1. Technical Field
This invention relates generally to the control of power supplied to a light source and other functions in an electronic device and, more particularly, to the use of light sensors to control the power supplied to such light source and the operation of such functions.
2. Description of the Background
Portable electronic devices, such as cellular phones and personal digital assistants, commonly include displays that are illuminated to facilitate interaction with a user. One challenge that arises with the illumination of such displays is the requirement to conserve energy in order to prolong battery life. Therefore, it is generally desirable to minimize power used to illuminate the display. However, it is also desirable to provide sufficient illumination to the display so that a user can operate the device in varying ambient light levels. In addition, to further prolong battery life, it is also desirable to illuminate the display only when a user is detected in a certain proximity to the device.
Therefore, a need has arisen for suitable sensors that can be integrated with existing electronic devices and that can be used to sense ambient light conditions and for proximity detection.
In one example of a prior device, an integrated circuit package includes a light source and an integrated circuit die with a sensor. The light source and the sensor are angled such that light emitted from the light source illuminates the field of view of the sensor. A single-piece substrate of the integrated circuit package has a nonlinear surface that defines the desired light source-to-sensor angle. The nonlinear surface includes one or more sharp bends or regions of curvature to provide the target relationship between illumination and sensing. The integrated circuit die is fixed to a first area of the single-piece substrate, while the light source is fixed to a second area. In this example, manufacturing costs are increased due to the requirement of a nonlinear surface to define the necessary angles. Further, the integrated circuit package is not used to sense ambient light conditions.
In another example of a prior device, an integrated proximity and light sensor includes an infrared light source and an infrared light detector. In this example, the infrared light detector senses infrared light emitted by the light source and reflected off of objects for proximity detection and further senses infrared light when the light source is turned off for ambient light detection. However, the use of infrared light for ambient light detection does not adequately match visible ambient light seen by the human eye, and therefore, an electronic device that incorporates such a sensor may not provide sufficient illumination to a display so that a user can operate the device in varying ambient light levels.